back to The Dragon
Here is a nice example that the dragon and the black raven both symbolize the first stage of the Great Work, Nigredo or Blackness.
The vat with water is is a variant of the glass vase. Another term for the transformation of the Matter is cooking.
At the same time there is also a duality woven into those two figures. The black raven lies down on its back and symbolizes the Fixed; while the dragon above has wings and is situated in the vapors, and thus symbolizes the volatile. in the Great Work there is an ongoing process of volatilizing the Fixed and fixing the Volatile.